Commit ffd5cfca authored by Stanislav Fomichev's avatar Stanislav Fomichev Committed by Daniel Borkmann
Browse files

selftests/bpf: Excercise bpf_obj_get_info_by_fd for bpf2bpf 



Apparently, no existing selftest covers it. Add a new one where
we load cgroup/bind4 program and attach fentry to it. Calling
bpf_obj_get_info_by_fd on the fentry program should return non-zero
btf_id/btf_obj_id instead of crashing the kernel.

Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220804201140.1340684-2-sdf@google.com
parent 6644aabb

tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c

+95 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
#include <test_progs.h>

#include <network_helpers.h>

#include <bpf/btf.h>

#include "bind4_prog.skel.h"



typedef int (*test_cb)(struct bpf_object *obj);
@@ -407,6 +408,98 @@ static void test_func_replace_global_func(void) 
				  prog_name, false, NULL);

}



static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)

{

	struct bpf_prog_info info = {};

	__u32 info_len = sizeof(info);

	struct btf *btf;

	int ret;



	ret = bpf_obj_get_info_by_fd(attach_prog_fd, &info, &info_len);

	if (ret)

		return ret;



	if (!info.btf_id)

		return -EINVAL;



	btf = btf__load_from_kernel_by_id(info.btf_id);

	ret = libbpf_get_error(btf);

	if (ret)

		return ret;



	ret = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);

	btf__free(btf);

	return ret;

}



static int load_fentry(int attach_prog_fd, int attach_btf_id)

{

	LIBBPF_OPTS(bpf_prog_load_opts, opts,

		    .expected_attach_type = BPF_TRACE_FENTRY,

		    .attach_prog_fd = attach_prog_fd,

		    .attach_btf_id = attach_btf_id,

	);

	struct bpf_insn insns[] = {

		BPF_MOV64_IMM(BPF_REG_0, 0),

		BPF_EXIT_INSN(),

	};



	return bpf_prog_load(BPF_PROG_TYPE_TRACING,

			     "bind4_fentry",

			     "GPL",

			     insns,

			     ARRAY_SIZE(insns),

			     &opts);

}



static void test_fentry_to_cgroup_bpf(void)

{

	struct bind4_prog *skel = NULL;

	struct bpf_prog_info info = {};

	__u32 info_len = sizeof(info);

	int cgroup_fd = -1;

	int fentry_fd = -1;

	int btf_id;



	cgroup_fd = test__join_cgroup("/fentry_to_cgroup_bpf");

	if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))

		return;



	skel = bind4_prog__open_and_load();

	if (!ASSERT_OK_PTR(skel, "skel"))

		goto cleanup;



	skel->links.bind_v4_prog = bpf_program__attach_cgroup(skel->progs.bind_v4_prog, cgroup_fd);

	if (!ASSERT_OK_PTR(skel->links.bind_v4_prog, "bpf_program__attach_cgroup"))

		goto cleanup;



	btf_id = find_prog_btf_id("bind_v4_prog", bpf_program__fd(skel->progs.bind_v4_prog));

	if (!ASSERT_GE(btf_id, 0, "find_prog_btf_id"))

		goto cleanup;



	fentry_fd = load_fentry(bpf_program__fd(skel->progs.bind_v4_prog), btf_id);

	if (!ASSERT_GE(fentry_fd, 0, "load_fentry"))

		goto cleanup;



	/* Make sure bpf_obj_get_info_by_fd works correctly when attaching

	 * to another BPF program.

	 */



	ASSERT_OK(bpf_obj_get_info_by_fd(fentry_fd, &info, &info_len),

		  "bpf_obj_get_info_by_fd");



	ASSERT_EQ(info.btf_id, 0, "info.btf_id");

	ASSERT_EQ(info.attach_btf_id, btf_id, "info.attach_btf_id");

	ASSERT_GT(info.attach_btf_obj_id, 0, "info.attach_btf_obj_id");



cleanup:

	if (cgroup_fd >= 0)

		close(cgroup_fd);

	if (fentry_fd >= 0)

		close(fentry_fd);

	bind4_prog__destroy(skel);

}



/* NOTE: affect other tests, must run in serial mode */

void serial_test_fexit_bpf2bpf(void)

{
@@ -430,4 +523,6 @@ void serial_test_fexit_bpf2bpf(void) 
		test_fmod_ret_freplace();

	if (test__start_subtest("func_replace_global_func"))

		test_func_replace_global_func();

	if (test__start_subtest("fentry_to_cgroup_bpf"))

		test_fentry_to_cgroup_bpf();

}